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Development of Bridge Foundation Movement Criteria

Geotechnical engineers estimate foundation movements to design bridge foundations and report their findings to the bridge designer. The bridge designer will then evaluate total movements, including differential movements that can be tolerated to satisfy post-construction bridge performance and to mitigate future maintenance issues. However, the current AASHTO LRFD Bridge Design Specifications do not provide clear criteria for movement limitations. The Specifications indicate that "the tolerable movement criteria shall be established by either empirical procedures or structural analyses or by consideration of both". Clear criteria and guidance are needed to ensure more efficient bridge designs while protecting the short and long-term integrity of structures. The objectives of this research are to (1) develop a framework to determine the acceptable levels of bridge foundation movements based upon structure tolerance to total and differential movements considering service and strength limit states, and (2) propose revisions to the AASHTO LRFD Bridge Design Specifications. Foundation movement shall include vertical, horizontal, and rotational movements.